|GAO, LIANGLIANG - University Of Minnesota|
|Rouse, Matthew - Matt|
|MIHALYOV, PAUL - Washington State University|
|BULLI, PETER - Washington State University|
|PUMPHREY, MICHAEL - Washington State University|
|ANDERSON, JAMES - University Of Minnesota|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2017
Publication Date: 8/17/2017
Citation: Gao, L., Rouse, M.N., Mihalyov, P.D., Bulli, P., Pumphrey, M.0., Anderson, J.A. 2017. Genetic characterization of stem rust resistance in a global spring wheat germplasm collection. Crop Science. 57:1-15.
Interpretive Summary: Wheat stem rust is a devastating fungal disease of wheat. A strain of the wheat stem rust fungus known as Ug99 emerged in Uganda in 1999 and threatens global wheat production because it is able to infect nearly all wheat varieties. We assessed 2152 spring wheat lines for response to stem rust pathogen strains including Ug99. In addition, 6226 molecular markers were evaluated on these lines. Genome-wide association mapping identified 47 significant associations between the markers and resistance to stem rust. Of these associations 11 regions correspond to previously characterized stem rust resistance genes. We identified accessions with combinations of resistance genes that could be used in cultivar development. The resistance genes and associated markers can be used by wheat breeding programs to select for Ug99 resistant wheat varieties protecting the United States crop from yield losses caused by foreign and domestic strains of the stem rust pathogen.
Technical Abstract: Stem rust is considered one of the most damaging diseases of wheat. The recent emergence of the stem rust Ug99 race group poses a serious threat to world wheat production. Utilization of genetic resistance in cultivar development is the optimal way to control stem rust. Here we report association mapping of stem rust resistance in a global spring wheat germplasm collection (2,152 accessions) genotyped with the wheat iSelect 9K SNP array. Using a unified mixed model method (or QK method), we identified a total of 47 loci that are significantly associated with various stem rust resistance traits including field disease resistance and seedling resistance against multiple stem rust pathogen races including BCCBC, TRTTF, TTKSK (Ug99), and TTTTF. The 47 loci could be further condensed into 11 QTL regions based on linkage disequilibrium information among adjacent markers. We postulate that these QTLs represent known stem rust resistance genes including Sr2, Sr6, Sr7a, Sr8a, Sr9h, Sr13, Sr28, Sr36. We further employed a multi-locus mixed model to explore marker trait associations and identified two additional QTLs (one potentially represents Sr31) that are significantly associated with stem rust resistance against various races. Combinations of the most significant loci for each trait explained up to 38.6% of the phenotypic variance. Markers identified through this study could be used to track the genes or QTLs. Accessions with high number of resistance-associated alleles may serve as important breeding materials for stem rust resistance.